In small internal combustion engines utilizing a carburetor, such as those engines in a lawnmower, a snowblower, or other outdoor power equipment, the engines typically include a choke assembly that provides a rich fuel-air mixture in the intake manifold upon start-up of the engine to sustain the combustion reaction, and a throttle assembly responsive to the speed of the engine and the load on the engine. In many small engines, the choke assembly is actuated manually.
In engines having an automatic choke assembly, such as those where the choke opening is controlled by a thermally responsive mechanism or where a self-relieving choke is utilized, fluctuating air pressure within the carburetor can cause a choke valve in the choke assembly to flutter after the choke has opened. While in certain engine operating conditions some amount of flutter may be desired, uncontrolled flutter in automatic choke devices can adversely affect the operation of the engine, such as by causing engine surging and increased component wear and fatigue within the engine.